The objective of this proposal is to understand more fully the etiology of the two major histologic types of brain cancer - gliomas and medulloblastomas - in young children. Restricting the cases to children aged 0-5 will allow an effective study of genetic predisposition, parental exposure to mutagens prior to the child's conception, and gestational exposure to carcinogens as possible risk factors. Ultimately, knowledge of etiologic factors may allow prevention of early detection of these tumors. The investigators will perform the case-control study through the Childrens Cancer Study Group, a cooperative group of 32 pediatric hospitals and their affiliates in the U.S. and Canada. Patients diagnosed wth a glima or medulloblastoma before their sixth birthday and registered with CCSG will constitute the cases. Newly diagnosed brain tumor patients registered with CCSG represent approximately 60% of all such patients in the U.S. Controls will be selected by the method of random digit dialing developed by us with one control per case matched on birth date (plus or minus 1 year), race, area code, exchange and next 2 digits of the telephone number. Demographic data, history of index pregnancy, parental reproductive history, parental occupational history, household exposure history, and family medical history will be collected in telephone interviews of the parents of each case matched control. The literature and our own data provided the hypotheses to be tested: compared to controls, young children with brain tumors have a higher frequency of 1) family history of seizures, cancers of the nervous, hematopoietic and lymphoid systems, or childhood cancers, 2) preconception exposures to paints, solvents and metals through paternal occupation and 3) gestational exposure to alcohol, other neurally active drugs, hair coloring products, N- nitroso containing substances, farm-related exposures, or metals. The pattern of associations is not expected to be the same for glioma and medulloblastoma. This study will be larger in size for each of the two major histologic types and narrower in age range than any previous studies of childhood brain cancer but may also be expected to shed light on the etiology of brain tumors in older children and adults.